1. Field of the Invention
The present invention relates to an electrical connector for electrically connecting an electronic package such as a pin grid array (PGA) chip with a circuit substrate such as a printed circuit board (PCB), and more particularly to an electrical connector providing accurate positioning of conductive contacts therein.
2. Description of the Related Art
Conventional central processing unit (CPU) sockets have contacts received in passageways of an insulative housing, for electrically connecting CPUs to PCBs. The contacts have engaging portions extending from one or two side edges thereof. The thickness of one whole engaging portion is approximately equal to the width of a fastening recess of each passageway. Thus the engaging portions are firmly held in the passageway, and the contact is securely fixed in the housing.
The trend toward miniaturization of electrical connectors and the development of surface mount technology (SMT) both require precise positioning of the contacts in the passageways. Coplanarity of soldering portions of all contacts in a CPU socket is very important for achieving precise soldering by way of SMT, especially for a ball grid array (BGA) connector. Conventional contacts are too small to be accurately inserted into the passageways of a housing of a BGA socket. Small gaps remain between interferential engaging portions of each contact and walls of the housing at a fastening recess of each passageway. In addition, the contacts may be inaccurately installed in the corresponding passageways during assembly of the BGA connector. For example, some contacts may be inserted at incorrect angles. This causes soldering portions of the contacts to be tilted relative to a PCB. The above-mentioned small gaps can be eliminated by ensuring that a thickness of the engaging portion of the contact is exactly equal to a width of the fastening recess of the passageway. However, insertion of the contact into the passageway is difficult and problematic. Forced insertion can result in plastic deformation of the housing at the passageway, and damage to the contact itself. Retaining the contacts in correct positions while still ensuring coplanarity of the soldering portions of the contacts has not yet been satisfactorily achieved. There remains unduly high risk of unstable connection between the contacts and the PCB. Contacts such as those disclosed in the U.S. Pat. Nos. 6,319,038, 5,797,774 and 5,299,950 bear out the above-described problems.
An improved CPU socket is desired to overcome the above-described shortcomings of conventional CPU sockets.